<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>过渡</title>
    <style>
        .box {
            width: 200px;
            height: 200px;
            background-color: tomato;
            /* 平滑过渡 */
            transition: all .5s ease-in .1s;
        }
        .box:hover {
            border-radius: 50%;
            /* 旋转 */
            transform: rotate(180deg);
            background-color: teal;
        }
    </style>
</head>
<body>
    <div class="box"></div>
</body>
</html>